Present methods for extracting polyamide polymers, including nylon, from commingled materials are neither energetically efficient nor economically viable. For example, numerous publications describe dissolving polyamide polymers in formic acid. See, e.g., U.S. Pat. Nos. 3,006,867; 3,749,698 and 5,994,417, and GB Patent Nos. 542128; 838668 and 1009592. However, these processes require heat sufficient for vaporization or distillation to remove the solvent and recover the polymer, which requires energy input and also degrades the quality of the polymer.
Antisolvent strategies for precipitation of polyamide polymers have also been described. See, e.g., U.S. Pat. Nos. 3,006,867 and 5,994,417, and GB Patent Nos. 542128; 838668 and 1009592. However, the published processes require energy input to provide heat sufficient for vaporization or distillation, or to provide temperatures and/or pressures sufficient to maintain the antisolvent at supercritical phase. Moreover, the polyamide polymer oftentimes precipitates in a form that can not be readily manipulated or used (e.g., as sticky globs).
There remains a need for energetically and economically viable methods to recover polyamide polymers from commingled materials.